Direct solidification of bulk ultrafine-microstructure eutectic high-entropy alloys with outstanding thermal stability

Although nanostructured (NS) and ultrafine-microstructure (UFM) materials possess excellent mechanical properties, how to manufacture bulk NS and UFM materials with minimum cost via direct casting remains challenging. Here, we report an efficient strategy to prepare bulk UFM alloys via the direct solidification method for eutectic high-entropy alloy (EHEA). As a proof of concept, we designed CoCrFeNiNb0.45 EHEA and achieved complete bulk UFM ingot with weight of 2.5 kg, demonstrating an ultrafine-lamellar microstructure. The as-cast alloy shows outstanding thermal stability and hardness up to 1100 degrees C. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.